Luminous spot shrinking system employing overlapping standing waves



May 23, 1967 v. CARNEY LUMINOUS SPOT SHRINKING SYSTEM EMPLOYING OVERLAPPING STANDING WAVES 4 Sheets-Sheet 1 Filed April 5, 1965 m QI May 23, 1967 I Filed April 5, 1963 V L. CARNEY OVERLAPPING STANDING WAVES 4 Sheets-Sheet 2 LUMINOUS SPOT HRINKING SYSTEM EMPLOYING M y 1967 v. L. CARNEY LUMINOUS SPOT SHRINKING SYSTEM EMPLOYING OVERLAPPING STANDING WAVES Filed April 5, 1963 4 Sheets-Sheet 3 INVENTOR WM 1, 6 BY 7 United States Patent Office 3,321,633 Patented May 23, 1967 3,321,633 LUMINOUS SPOT SHRINKING SYSTEM EMPLOY- IN G OVERLAPPING STANDING WAVES Vincent L. Came Silver Spring, Md. (2839 W. Palmer St., Chicago, Ill. 60647) Filed Apr. 5, 1963, er. No. 270,941 18 Claims. (Cl. 250-213) This invention relates to display devices and more particularly relates to a method and apparatus for controlling the size of a movable luminous spot used to create images in display devices.

In many types of display devices such as the CRT (cathode ray tube) used in television receivers an image is created by a luminous spot which is controlled in position and in intensity by electrical signals. The luminous spot rapidly scans the surface of the display device varying in intensity as it moves so as to create a complete image.

It is desirable for the luminous spot to be small. If it is too large the image will be blurred. This is a serious problem in electroluminescent and photoluminescent displays: particularly those that use standing waves or travelling waves of voltage and current to excite the electroluminescent material or photoluminescent material into emitting light so as to form a luminous spot. The standing waves created with most pulses generators are wider than desired and cause a large luminous spot to appear. Accordingly, it is an object of this invention to provide an improved display device.

It is a further object of this invention to provide a movable luminous spot on a surface which may be modulated in size.

It is a further object to provide a display device on which images are formed 'by a luminous spot which is controlled in size, intensity, color and position by electrical signals.

It is a further object to provide a display device in which a controllable luminous spot is formed from the interaction of standing waves on a plurality of elements.

In accordance with the above and further objects of the invention, a method and apparatus are provided for controlling the size of a luminous spot on the surface of a display device of the type in which light is emitted by a photolurninescent or electroluminescent material that is energized by a standing wave of electrical energy. Two layers of luminescent material are used: one of which is energized by a standing wave to emit light and to thereby illuminate an area of the second layer, the second layer being energized only by the combination of light from the first layer and another standing wave of electrical energy. The illuminated area and the standing wave on the second layer overlap in a small area. This small area emits the light that is visible from the surface of the display device.

The invention and the above noted and other features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawings in which:

FIGURE 1 is a flow diagram illustrating one stage in the operation of an embodiment of the invention;

FIGURE 2 is a flow diagram illustrating another stage in the operation of an embodiment of the invention;

FIGURE 3 is a partial schematic block diagram of an embodiment of the invention showing an off-set means, wave-front straightener and part of a display device in a sectional view;

FIGURE 4 is a perspective view of an embodiment of an embodiment of the invention;

FIGURE 5 is a perspective view of another embodiment of the invention;

FIGURE 6 is a cross-sectional view of the display device of this embodiment of the invention;

FIGURE 7 is a cross-sectional front view of another embodiment of this invention; and

FIGURE 8 is a cross-sectional side view of this embodiment of the invention.

Referring now in particular to FIGURE 1 a flow diagram illustrating one stage in the operation of an embodiment of the invention is shown having a first flat energy conducting element 10, and a second flat energy conducting element 12 which is positioned above and parallel to the first flat energy conducting element 10. Three wave fronts of energy 14, 16 and 18 are shown traversing the first flat energy conducting element 10.

The wave front 14 is moving from the front of the first energy conducting element 10 to the back as indicated by the arrow 20. A shaded area 22 is shown on the second flat energy conducting element 12 which is above and corresponds in shape to the wave front 14 on the first energy conducting element 10. The wave front 16 is moving from left to right on the first energy conducting element 10 as indicated by the arrow 24, and a shaded area 26 is shown on the second flat energy conducting element 12 which is above and corresponds in shape to the wave front 16 on the first energy conducting element 10. The wave front 18 is moving from right to left on the first energy conducting element 10 as indicated by the arrow 28 and a shaded area 30 is shown on the second fiat energy conducting element 12 which is above and corresponds in shape to the wave front 18 on the first energy conducting element 10. The wave front 16 and the wave front 14 intersect over the area 32 on the first energy conducting element 10 to form an area of higher energy from the sum of the energies of the two wave fronts 14 and 16, and the wave front 18 intersects the wave front 14 over the area 34 to form a second area of high energy.

Three wave fronts 36, 38 and 40 are also propagated along the second flat conducting element 12. The wave front 36 is moving from the front of the second energy conducting element 12 to the back as indicated "by the arrow 42 and is slightly in front of the shaded area 22 so as to overlap it across an area 44. The wave front 38 is moving from left to right on the second energy conducting element 12 as indicated by the arrow 46 and is slightly in front of the shaded area 26 so as to overlap it across an area 48. The wave front 40 is moving from right to left on the second energy conducting element 12 as indicated by the arrow 50 and is slightly in back of the shaded area 36 so as to overlap it across an area 52.

FIGURE 2 shows the energy conducting elements 10 and 12 at another stage in the operation of .an embodiment of the invention. The Wave fronts 16 and 18 have overlapped to form the additive standing wave 54 which intersects the wave front 14 over the area 56. Shaded areas 58, 60 and 62 are shown on the second flat energy conducting element 12 which are above and correspond in shape to the wave front 14, the standing wave 54 and the standing wave 56 respectively on the first energy conducting element 10.

Similarly, the wave fronts 38 and 40 on the second energy conducting element 12 intersect to form the standing wave 64 which overlaps the shaded area 60 in an area 66. At this time the wave front 36 overlaps the shaded area 58 in an area 68.

It can be seen that the shaded area 62 on the energy conducting element 12 which is above the standing wave 56 formed by the intersection of the wave fronts 14, 16 and 18 on the first energy conducting element 10 overlaps the standing wave formed on the second energy conducting element 12 by the wave fronts 36, 38 and 40 in the darkened area 70. The size of this area '70 is determined by the amount of overlapping between the wave fronts of the first energy conducting element and the second energy conducting element 12.

FIGURE 3 illustrates the manner in which the principle shown by the flow diagrams of FIGURE 1 and FIGURE 2 may be used to control the size of a luminous spot used to create an image on a display just as the overlapping wave fronts control the size of the shaded area 78 in FIGURE 2. FIGURE 3 is a schematic block circuit diagram of part of an embodiment of the invention showing a partial sectional view of the wave front straighteners, off-set means and flying spot shrinker.

A nsec. (nanosecond being 10 seconds) pulse generator 72 is electrically connected to the diiferentiator 74 to provide submillimeter voltage pulses for the wave fronts. The nsec. pulse generator 72 may be of the spark gap generator type such as that described by J. B. Gunn in the article Bouncing Ball Pulse Generator in the I.B.M. Technical Disclosure Bulletin, Vol. 5, No. 8, January 1963, or of the regenerative pulse generator type described by C. C. Cutler in The Regenerative Pulse Generator; Proc. Inst. Radio Engrs; 1955, 43, 140-8. The differentiator 74 may be a shorted section of transmission line. The voltage pulses may also be generated by a vacuum tube of the type described by E. W. Ernst and H. von Foerster in the article Electron Bunches of Short Time Duration; Journal of Applied Physics; 1954, 25, 674-5.

The input of the gate 76 is electrically connected to the output of the differentiator 74. A low frequency A.C. (alternating current) generator 78 has its output electrically connected to the gate control of the gate 76. It provides an AC. output that is adjustable between 60 and 1000 c.p.s. (cycles per second) to the gate 76. If color changes are desired a variable frequency generator may be used instead of the constant frequency generator.

The gate 76 includes the resistor 80 which is electrically connected at one end to the first output terminal of the dilferentiator 74 and at the other end to the cathode of diode 82, to the anode of diode 84, and to a first input terminal of variable delay 86. The anode of diode 82 is electrically connected to the anode of diode 88 through conductor 90 and to the first end of resistor 92; the cathode of diode 84 is electrically connected to the cathode of diode 94 and to the first end of resistor 96. The cathode of diode 88 and the anode of diode 94 are each connected to a first output terminal of the low frequency A.C. generator 78 through conductor 98. The second ends of resistors 92 and 96 are electrically connected to each other to the second output terminal of the differentiator 74, to the second input terminal of variable delay 86, and to the second output terminal of the low frequency A.C. generator 78.

The nsec. pulse generator 72 provides rectangular voltage pulses of short time duration to the diiferentiator 74. The differentiator 74 differentiates both the rising and falling edges of the voltage pulses from the nsec. pulse generator 72 to provide a plurality of positive and negative submillimeter pulses to the gate 76.

When the polarity of the low frequency A.C. generator 78 is such that conductor 98 is positive, the gate 76 only passes positive submillimeter pulses from the differentiator 74 to the variable delay 86. This is because both diode 82 and diode '84 offer a high resistance to positive pulses, but the diode 82 offers a low resistance to negative pulses and shunts them. Diode 84, which would normally offer a low resistance to positive pulses is blocked by the positive voltage from the low frequency A.C. generator 78 which is conducted through conductor 98, and diode 94 to the cathode of the diode 84.

When the polarity of the low frequency A.C. generator 78 is such that conductor 98 is negative, the gate 76 only passes negative submillimeter pulses from the differentiator 74 to the variable delay 86. This is because both diode 82 and diode 84 offer a high resistance to negative pulses but diode 84 offers a low resistance to positive pulses and shunts them. Diode 82, which would normally offer low resistance to negative pulses, is blocked by the negative voltage from the low frequency A.C. generator 78 which is conducted through conductor 98, and diode 88 to the anode of diode 82.

The variable delay 86 receives the submillimeter voltage pulses and conducts them to the wave front straightener and off-set means 100 after a time delay determined by the voltage applied to terminal 103. The variable delay 86 may be of the types described in the copending patent application of Vincent L. Carney, Ser. No. 272,820, filed Apr. 5, 1963, and entitled Electroluminescent Scanning and Display System, now US. Patent No. 3.277339. The wave front straighteners form the submillimeter voltage pulses into straight wave fronts as described in the aforesaid patent by Vincent L. Carney. They also act as off-set means to delay the wave fronts on the top pair of wave front straighteners by a different amount so that the wave front on the bottom and top Wave front straighteners partially overlap each other as described above with reference to FIGURE 1 and FIGURE 2. These wave fronts are conducted to the display surface 102.

The wave front straighteners and off-set means include the four separate, overlying conductors 104, 106, 108 and 110. A first output terminal 113 of the variable delay 86 is electrically connected to the top conductor 104 and the third conductor from the top 108, which conductors are electrically in parallel. The other output terminal 115 of the variable delay 86 is electrically connected to the second conductor from the top 106 and t0 the bottom conductor 110, which conductors are also in parallel.

The wave front straighteners pair 104 and 106 are electrically connected to the flat conductors 112 and 114 of the display surface 102. There are two overlying conductors, curved downward in the center with the top conductor having a greater curvature than the bottom conductor. The two conductors are insulated from each other. The widest portion is connected to the display surface 102 and the conductors taper to a point at the other end where they are electrically connected to the variable delay 86. The curvature increases the electrical path from the terminal point to the wide edge and changes the velocity of propagation so that the voltage applied at the terminal takes the same amount of time to arrive at each point of the side of the display device surface 102 so as to form a straight line as explained in the aforesaid patent of Vincent L. Carney, entitled Electroluminescent Scanning and Display System.

The wave front straightener pair 108 and 110 are electrically connected to the fiat conductors 116 and 118 respectively on the display surface. They are constructed in the same manner as the Wave front straighteners 104 and 106 described above. As explained in connection with FIGURE 1 and FIGURE 2, the wave front transmitted to the conductors 112 and 114 by the wave front straighteners 104 and 106 must overlap the 'wave front transmitted to the conductors 116 and 118 of the display device surface 102 by the Wave front straighteners 108 and 110. The wave front on the top wave front straightener pair is slightly in front of the wave front on the bottom wave front straightener on one edge of the display device surface 102 and the wave front on the top wave front straightener is slightly behind the wave front on the bottom wave straightener on the opposite edge. The two pairs of wave front straighteners comprise the off-set means since they cause the top wave front to be off-set from the bottom wave front. Of course, separate delays could be used with wave front straighteners having the same amount of delay instead of incorporating the off-set delay with the wave-straightening delay.

The standing wave formed by the repeated intersection of the voltage waves from the three sides of the display surface 102 on bottom conductors 116 and 118 causes a luminous phosphor 128 placed between these conduc tors to emit a spot of light in the manner described in the aforesaid patent of Vincent L. Carney, entitled Electroluminescent Scanning and Display System.

A layer of photoconductive material 122 is in contact with the conductor 114 of the top pair of conductors on the opposite side from conductor 116 of the bottom pair of conductors. A layer of luminous phosphors 124 is placed between the layer of photoconductive material 122 and the conductor 112.

The spot of light emitted by the layer of luminous phos phor 12%) caused by the standing wave of voltage on bottom conductors 118 and 116 passes through transparent conductors 116 and 114 and impinges on the photoconductive layer 122. In the absence of a spot of light from the layer of luminous phosphor 120, the standing wave formed on the top conductors 114 and 112 does not cause a spot of light to be emitted from the layer of luminous phosphor 124 since the voltage is dropped mainly across the layer of photoconductive material 122 which separates the layer of luminous phosphor 124 from the top conductor 114.

However, the portion of the standing Wave that is formed on the top pair of conductors 112 and 114 overlaps the standing wave that is formed on the bottom pair of conductors 116 and 118. Consequently, voltage of the standing wave that is formed on the top pair of conductors is dropped primarily across the layer of luminous phosphor 124 over the area that overlaps the standing wave on the bottom pair of conductors because the light emitted from the layer of luminous phosphor 120 reduces the resistance of the photoconductive material 122, and the voltage of the standing wave that is formed on the top conductors over the remainder of the area is dropped primarily across the high resistance photoconductive layer 122. The layer of luminous phosphor 124 then emits a spot of light through transparent conductor 112, which spot of light has a smaller area than the standing waves on either the bottom or top conductor pairs in the manner illustrated by FIGURE 1 and FIG- URE 2.

The transparent conductors and the layer of luminous phosphor may be prepared in the manner described in the aforesaid patent of Vincent L. Carney. The photoconductive material may be prepared as described in the copending patent application of Vincent L. Carney, entitled Transmission Line Display System, Ser. No. 273,260, filed Apr. 5, 1963. Of course, either electroluminescent materials or photolurninescent materials may be used for the luminous phosphor with the modifications described in the aforesaid patent and application of Vincent L. Carney, including irradiation of the photoluminescent material with ultraviolet light. Also, colour or black and White may be obtained. A single conductor may be used in place of the conductors 114 and 116, but usually this is not done since the conduct-or is plated on one side of a glass plate.

A perspective view of an embodiment of the invention is shown in FIGURE 4, having a pulse generator circuit 126, three variable delay units 128, 130 and 132, three wave front straighteners and off-set means 134, 136 and 138, and a display surface 140. The pulse generator circuit 126 is one of the types described with respect to FIGURE 3. If an electroluminescent display surface is used it will include a low frequency A.C. generator and a gate for periodically changing the polarity of the voltage wave fronts. If photoluminescent material is used in the display surface the gate and low frequency A.C. generator are not needed, but a source of ultraviolet light 141 and DC. (direct current) pulses with a superimposed RF signal for color are used.

The pulse generator circuit 126 has its output electrically coupled to the inputs of each of the variable delays 128, 130 and 132. The amount of delay imparted to the pulses from the pulse generator circuit 126 by the variable delays 128, 130 and 132 depends upon the magnitude of the input signal received on their respective delay control terminals 142, 144 and 146. The amount of delay imparted to the pulses controls the location of the intersection of these pulses to form a luminous spot on the display surface 140.

One output of the variable delay 128 is electrically coupled to a first wave front straightener 148 of the top pair of wave front straighteners and to a first wave front straightener 150 of the bottom pair of wave front straighteners in the wave front straightener and off-set means 134. The other output of the variable delay 128 is electrically coupled to the second Wave front straightener 152 of the top pair of wave front straighteners and to the second wave front straighteners 154 of the bottom pair of wave front straighteners in the wave front straightener and off-set means 134. The top pair of wave front straighteners and the bottom pair of wave front straighteners together form the off-set means. The bottom pair of wave front straighteners 150 and 154 are longer and therefore provide more delay to the wave fronts than the top pair causing the top wave fronts to overlap and precede the bottom wave fronts.

The variable delay 130 is electrically coupled to the wave front straightener and off-set means 136 in the same manner as the variable delay 128 is connected to the wave front straightener and off-set means 134. Similarly, one output of the variable delay 132 is electrically coupled to a first wave front straightener 156 of the top pair of wave front straighteners and to a first Wave front straightener 158 of the bottom pair of wave front straighteners in the wave front straightener and off-set means 138. The other output of the variable delay 128 is electrically coupled to the second wave front straightener 160 of the top pair of wave front straighteners and to the second wave front straightener 162 of the bottom pair of wave front straighteners in the wave front straightener and off-set means 138. However, the top pair of wave front straighteners 156 and 160 are longer and provide more delay to the wave fronts than the bottom pair causing the bottom wave fronts to overlap and precede the top wave fronts, which is the opposite result from that of wave front straightener and off-set means 134.

The repeated intersection of wave fronts from the bottom pairs of Wave front straighteners on the three sides of the display surface 140 cause a standing Wave of voltage. to appear across the bottom conductors 164 and 166 to which the bottom wave front straighteners are electrically coupled. This standing Wave causes a spot of light to be emitted from the layer of luminous phosphor 168. The spot of light from the luminous phosphor 168 passes through the transparent conductors 166 and 170 and reduces the resistance of the photoconductive layer 172 directly above it. The repeated intersection of the Wave fronts from the bottom pairs of wave front straighteners on the three sides of the display surface 140 cause a standing wave of voltage to appear across the top conductors 170 and 174. This standing wave of voltage overlaps the standing wave of voltage on the bottom pair of conductors so that it is partially across both an area of low resistance and partially across an area of high resistance in the photoconductive layer 172. In the area of low resistance of photoconductive layer 172 the layer of luminous phosphor 175 has most of the voltage dropped across it and emits a spot of light that is smaller than either of the standing waves on the bottom conductors or the top conductors.

FIGURE 5 is a perspective view of another embodiment of the invention, having a pulse generator 176, variable delay lines 178, 180, 182 and 184, a bottom or primary transmission line 186, and a top or secondary transmission line 188. The pulse generator 176 provides pulses to each of the variable delay lines 178, 180, 182 and 184.

The bottom transmission line 186 receives voltage pulses on a first end 190 from the variable delay line 17 8 to which it is electrically coupled and on a second end 192 from the variable delay line 188 to which it is electrically coupled. The top transmission line 188 receives voltage pulses on a first end 194 from the variable delay line 182 to which it is electrically coupled and on a second end 196 from the variable delay line 184 to which it is electrically coupled.

The voltage pulses that enter the bottom transmission line 186 at the ends 190 and 192 intersect along the line. Repeated intersections from a succession of voltage pulses causes a standing wave of voltage to be formed. The dielectric material in the bottom transmission line 186' contains a luminous phosphor which emits light in the vicinity of this standing wave. This phenomena and the transmission lines used in it are described more completely in the copending application of Vincent L. Carney, entitled Transmission Line Display System, Ser. No. 273,- 260, filed Apr. 5, 1963 now abandoned.

A second series of voltage pulses entering the top transmission line 188 at the ends 194 and 1% intersect to form a second standing wave of voltage. The dielectric material in the top transmission line 188 contains a layer of photoconductive material on the bottom and a layer of luminous phosphor which emits light in the vicinity of this standing wave providing the photoconductive material has a low resistance resulting from light originating in the bottom transmision line 186.

The standing waves on the bottom transmission line 186 and the top transmission line 188 are frequently long because of the difficulty of generating pulses of submillimeter width. This causes the spot of light emitted from the bottom transmission line 186 to be long. However, the bottom transmission line 186 is covered by the top transmission line 188, which forms the surface of the display. The top transmission line 188 only emits light in those areas where it both receives light from the bottom transmission line 186 which is perpendicular to it and where it has a standing wave of its own. Since the two transmission lines are perpendicular this will be a square shaped spot of light having the width of the transmission line. The location of this spot of light may be changed by changing the amount of delay in the variable delay lines 178, 180, 182 and 184.

A cross-sectional view of this embodiment of the invention is shown in FIGURE 6. The bottom transmission line 19 8 is wound around a fiat insulator 200. This transmission line comprises a Mylar casing 202, a bottom conductor 204, a top transparent conductor 206, and a layer of luminous phosphor 208 sandwiched between the top conductor 205 and the bottom conductor 204.

The top transmission line 210 is wound around the outside of the bottom transmission line 198 and perpendicular to it. The top transmission line 210 comprises a Mylar casing 212, a top transparent conductor 214, a layer of luminous phosphor 216 under and in contact with the top transparent conductor 214, a layer of photoconductive material 218 under and in contact with the layer of luminous phosphor 216, and a bottom transparent conductor 220 under and in contact with the layer of photoconductive material 218.

A cross-sectional front view and a cross-sectional side view of another embodiment of the invention are shown in FIGURE 7 and FIGURE 8, respectively. This embodiment utilizes strip line transmission lines.

The bottom transmission line 222 comprises a base conductor 224, a dielectric layer 226 including a luminous phosphor on top of the flat base conductor 224, and a continuous strip line conductor 228 wound on top of the dielectric layer 226. Voltage pulses applied to the strip transmission line causes a standing wave to be created and cause a spot of light to be emitted.

The top transmission line 230 comprises a transparent base conductor 232, a layer of photoconductive material 234 on top of the transparent base conductor 232, a layer of dielectric material 236 containing a luminous phosphor,

and a continuous strip line conductor 238 wound on top of the layer of dielectric material 236 and having parallel sides that are each perpendicular to the transmission line 228. Voltage pulses applied to the strip line cause a standing wave to be created and causes a spot of light to be emitted where this standing wave crosses the spot of light created by the bottom transmission 222.

The above described method and apparatus provide a system for controlling the size of a luminous spot on a display surface. This system is particularly well adapted for use in conjunction with the travelling wave type of display device. It has the same advantages of being sturdy, utilizing standing waves, having a small size, and being solid state.

Although in the above embodiments the invention has been described as a means for reducing the size of a luminous spot, it is obvious that it can also be used to reduce the number of luminous spots. If different frequencies are used on the top and bottom energy conducting surfaces and the frequencies are high enough so that multiple standing waves are formed, light will be emitted only where the standing waves overlap. In this manner advantage can be taken of devices which can generate continuous waves of submillimeter Width.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is: 1. A method of creating a luminous spot comprising the steps of transmitting a first plurality of waves of energy fro-m difierent points in a first plane, whereby a first standing wave of high energy will be formed;

transmitting -a second plurality of Waves of energy from different points in a second plane, parallel to said first plane, whereby a second standing Wave of high energy will be formed; and

converting the portion of said first standing wave that overlaps said second standing wave to light.

2. A method of creating a luminous spot comprising the steps of:

transmitting a voltage pulse from one end of a first transmission line; tnansmitting a voltage pulse from the other end of said first transmission line, whereby a first standing wave of energy is formed on said first transmission line;

transmitting a voltage pulse from one end of a second transmission line which is adjacent to and at an angle with said first transmission line;

transmitting a voltage pulse from the other end of said second transmission line, whereby a second standing wave of energy is formed on said second transmission line; and

converting the portion of said first standing wave that overlaps said second standing wave to light.

3. A method of creating a luminous spot on a surface of a transducer having a first conductor, a first layer of electroluminescent material in front of said first conductor, a conductor means in front of said first layer of electroluminescent material, a layer of photoconductive material in front of said conductor means, a second layer of electroluminescent material in front of said layer of photoconductive material and a second conductor in front of said second layer of electroluminescent material with said conductor means and said second conductor being capable of passing light, comprising the steps of:

applying first electromagnetic energy across said first conductor and said conductor means at a first spot on said transducer;

applying second electromagnetic energy across said first conductor and said conductor means at -a second spot on said transducer;

g applying third electromagnetic energy across said first conductor and said conductor means at a third point on said transducer, whereby a first standing wave of high electromagnetic energy is formed at a first area so as to cause said first layer of electroluminescent material to emit a spot of light at said first area and thereby reduce the resistance of said photoconductive layer at that point; applying fourth electromagnetic energy across said second conductor and said conductor means at a point on said transducer;

applying fifth electromagnetic energy across said second conductor and said conductor means at another point on said transducer;

applying sixth electromagnetic energy across sairl second conductor and said conductor means at still another point on said transducer, whereby a second standing wave of high electromagnetic energy is formed at a second area on said transducer which partially overlaps said first area so that light is emitted from said second layer of electroluminescent material Where said second area overlaps said first area.

4. A method of creating a luminous spot on a surface of a transducer having a first conductor, a layer of luminescent material in front on said first conductor, a second conductor in front of said layer of luminescent material, a layer of photoconductive material in front of said second conductor, a layer of photoluminescent material in front of said layer of photoconductive material and a third conductor with said second and third conductors being transparent, comprising the steps of:

applying first electromagnetic energy across said first and said second conductors at a first spot on said transducer;

applying second electromagnetic energy across said first and said second conductors at a second spot on said transducer;

applying third electromagnetic energy across said first and said second conductor at a third point on said transducer, whereby a first standing wave of high electromagnetic energy is formed at a first area so as to cause said layer of luminescent material to emit a spot of light at said first area and thereby reduce the resistance of said photoconductive layer at that point;

irradiating said layer of photoluminescent material with ultraviolet light;

applying fourth electromagnetic energy across said second and said third transparent conductors at a point on said transducer;

applying fifth electromagnetic energy across said second and said third transparent conductors at another point on said transducer;

applying sixth electromagnetic energy across said second and said third transparent conductors at still another point on said transducer, whereby a second standing wave of high electromagnetic energv is formed at a second area on said transducer which partially overlaps said first area so that light is emitted from said second layer of photoluminescent material where said second area overlaps said first area.

5. A method of creating a luminous spot on a surface of a transducer having a first conductor, a first layer of luminous phosphor in front of said first conductor, a second conductor in front of said first layer of luminous phosphor, a layer of photoconductive material in front of said second conductor, a second layer of luminous phosphor in front of said layer of photoconductive material and a third conductor in front of said second layer of luminous phosphor with said second and third conductors being transparent, comprising the steps of:

applying first microwave energy across said first and second conductors at first, second and third points on said transducer, whereby a first plurality of 10 standing waves of high energy are formed so as to cause said first layer of luminous phosphor to emit light from a first plurality of spots and thereby to reduce the resistance of said photoconductive layer at said first plurality of points;

applying second microwave energy having a difierent frequency than said first microwave energy across said second and said third conductors at a first, second and third points on said transducer, whereby a second plurality of standing waves of high electromagnetic energy are formed so that light is emitted by said second layer of luminous phosphor at points Where said second plurality of standing waves overlaps said first plurality of standing waves.

6. A method of creating a luminous spot on a surface of a transducer having a first transmission line, comprising a first layer of luminous phosphor, and bent so that sections of said first transmission line are parallel and adjacent to other sections of said first transmission line in a first plane so as to form a surface and a second transmission line comprising a layer of photoconductive material and a second layer of luminous phosphor, bent so that sections of said second transmission line are parallel and adjacent to other sections of said second transmission line in a second plane parallel to said first plane and at an angle with said sections of said first transmission line, comprising the steps of transmitting microwave energy in two directions along said first transmission line, whereby a first plurality of standing waves are formed so as to cause said first layer of luminous phosphor to emit light at a plurality of points along said first transmission line; and

transmitting microwave energy in two directions along said second transmission line, whereby a second plurality of standing waves are formed so as to cause said second layer of luminous phosphor to emit light at points where a standing wave appears on said second transmission line that is just above a standing wave on said first transmission line.

7. A method of creating an image on a display surface of a transducer having a first conductor, a first layer of luminous phosphor in front of said first conductor, a second conductor in front of said first layer of luminous phosphor, a third conductor in front of said second transparent conductor, a layer of photoconductive material in front of said third transparent conductor, a second layer of luminous phosphor in front of said layer of photoconductive material and a fourth conductor in front of said second layer of luminous phosphor said second, third, and fourth conductors being transparent, comprising the steps of:

generating a plurality of voltage pulses having a short duration;

conducting said plurality of voltage pulses to a first point on said transducer along a first primary transmission path and along a first secondary transmission path;

conducting said plurality of voltage pulses to a second point on said transducer along a second primary transmission path and along a second secondary transmission path;

conducting said plurality of voltage pulses to a third point on said transducer along a third primary transmission path and along a third secondary transmission path;

applying said plurality of voltage pulses from said primary transmission path to said three different points on said transducer across said first and said second conductors, whereby a first area of high standing voltage is formed on said transducer so as to cause said first layer of luminous phosphor to emit light; applying said plurality of voltage pulses from said secondary transmission path to said three different points on said transducer across said third and said fourth conductors, whereby a second area of high standing voltage is formed on said transducer; delaying said plurality of voltage pulses from said first primary and said third secondary transmission paths, whereby said first area of high standing voltage and said second area of high standing voltage are displaced from one another so as to partially overlap and form a final spot of light at their overlapping portion; 7

delaying said plurality of voltage pulses to one of said points on said transducer so as to cause the final spot of light to move in one direction; and

modulating the amplitude of said plurality of voltage pulses to vary the intensity of said emitted light.

8. A method of creating an image'on a display surface of a transducer having a first conductor, a first layer of electroluminescent material in front of said first conductor, a second conductor in front of said first layer of electroluminescent material, a third conductor in front of said second conductor, a layer of photoconductive material in front of said third conductor, a second layer of electroluminescent material in front of said layer of photoconductive material and a fourth conductor in front of said second layer of electroluminescent material said second, third, and fourth conductors being capable of passing light, comprising the steps of generating a plurality of voltage pulses having a short duration;

periodically changing the polarity of said voltage pulses;

conducting said plurality of voltage pulses to a first point on said transducer along a first primary transmission path and along a first secondary transmission path;

conducting said plurality of voltage pulses to a second point on said transducer along a second primary transmission path and along a second secondary transmission path;

conducting said plurality of voltage pulses to a third point on said transducer along a third primary transmission path and along a third secondary transmission path; applying said plurality of voltage pulses from said primary transmission path to said three different points on said transducer across said first and said second conductors, whereby a first area of high standing voltage is formed on said transducer so as to cause said first layer of luminous phosphor to emit light;

applying said plurality of voltage pulses from said secondary transmission path to said three different points on said transducer across said third and said fourth conductors, whereby a second area of high standing voltage is formed on said transducer;

delaying said plurality of voltage pulses from said first primary and said third secondary transmission paths, whereby said first area of high standing voltage and said second area of high standing voltage are displaced from one another so as to partially overlap and form a final spot of light at their overlapping portions;

delaying said plurality of voltage pulses to one of said points on said transducer so as to cause the final spot of light to move in one direction;

modulating the amplitude of said plurality of voltage pulses to vary the intensity of said emitted light; and modulating the frequency of said periodic changes in said polarity of said plurality of voltage pulses so as Y to vary the color of said emitted light.

9. A display device comprising:

first transducer means for emitting light in response to a first form of energy;

second transducer means, positioned so as to receive light from said first transducer means, for emitting light in response to the combination of light and said first form of energy; and

said energizing means comprises:

pulse generator means for generating voltage pulses having a pulse width that is short with respect to the width of said second transducer means; and

off-set means, electrically connected to said pulse generator means and to said first and second transducer means, for transmitting said voltage pulses to said first and second transducer means in a partially overlapping time relationship.

11. A display device according to claim 10, in which said first transducer means comprises:

a first conductor;

a layer of luminous phosphor in front of said first conductor; and

a second conductor in front of said layer of luminous phosphor, said second conductor being capable of passing light.

12. A display device according to claim 11, in which said second transducer means comprises:

a first transparent conductor;

a layer of photoconductive material in front of said first transparent conductor;

a layer of luminous phosphor in front of said layer of photoconductive material; and

a second transparent conductor in front of said layer of luminous phosphor.

13. A display device comprising:

first phosphor means for emitting light when an electrical voltage is dropped across it;

a first conductor in contact with one side of said first phosphor means and having a first pair of perpendicular axes the ends of which intersect the edges of said first conductor to form terminals;

a second conductor having one side in contact with the other side of said first phosphor means and having a second pair of perpendicular axes the ends of which intersect the edges of said second conductor to form terminals;

a layer of photoconductive material in contact with the other side of said second conductor;

second phosphor means, in contact with said layer of photoconductive material, for emitting light when an electrical voltage is dropped across it;

a third conductor in contact with said second phosphor means and having. a third pair of perpendicular axes the ends of which intersect the edges of said third conductor to form terminals said second and third conductors being transparent;

first, second and third fixed delay means, electrically connected to said first, second and third conductors at three corresponding terminals of said first, second and third conductors, for forming straight wave fronts from said electric voltages which partially overlap between said first and third conductors;

generator means for generating voltage pulses;

first variable delay means, having its input electrically connected to said generator means and having its output electrically connected to said first fixed delay means, for conducting said voltage pulses to said first, second and third conductors with a predetermined delay;

second variable delay means, having its input electrically connected to said generator means and having its output electrically connected to said second 13 fixed delay means, for conducting sa-id voltage pulses to said first and second conductors with a predetermined delay;

a fourth conductor connecting said generator means to said third fixed delay means, whereby two overlapping points of high standing voltage are formed across said first and second conductors and across said second and third conductors so that a spot of light is formed over their overlapping areas due to the reduction in the resistance of said photoconductive material over the light emitted in response to one of said points of high standing voltage; and

modulating means for modulating the amplitude of said voltage pulses so as to vary the intensity of said spot of light, I g

14. A display device comprising;

a primary transmission line bent between a first primary terminal and a second primary terminal and thereby having sections of said primary transmission line adjacent to other sections in a common plane so as to form a primary transmission line surface;

said primary transmission line having a layer of luminous phosphor within it, whereby voltages transmitted down said primary transmission line appear across said luminous phosphor;

a secondary transmision line bent between a first secondary terminal and a second secondary terminal and thereby having sections of said secondary transmission line adjacent to other sections in a common plane so as to form a secondary transmission-line surface parallel to said primary transmission line surface;

said sections of said secondary transmission line forming an angle with said sections of said primary transmission line;

said secondary transmission line having a layer of luminous phosphor and a layer of photoconductive material within it with said layer of photoconductive material being closest to said primary transmission-line surface;

pulse generator means, electrically coupled to said first and second terminals of said primary and secondary transmission lines, for applying pulses to said first and second terminals of said primary and secondary transmission lines, whereby said pulses will intersect on said primary transmission line to form an area of light which reduces the resistance of said layer of photoconductive material and will intersect on said secondary transmission to form an area of light over the portion of said display device where said voltage pulses intersect on both said primary transmission line and said secondary transmission line.

15. A display device according to claim 14, in which said primary and secondary transmission lines are strip line transmission lines.

16. In' a two-layer transducer of the type having a first layer that is capable of emitting light from one surface in response to electrical excitation across said first layer and having a second layer that is capable of emitting light from one surface in response to electrical excitation across said second layer and in response to light impinging on a second surface of said second layer which second surface is next to said one surface of said first layer, a method of controlling the size and position of a spot of light, comprising the steps of:

applying electrical pulses having a wave length shorter than the Width of said one surface of said first layer at a plurality of points on said first layer, whereby a first standing wave of electrical energy is formed on said first layer so that light is emitted from a spot on said one surface of said first layer, which light is incident on a spot of said second surface of said second layer; and

applying electrical pulses having a wave length shorter than the width of said one surface of said second layer of a plurality of points on said second layer and at times that will cause a second standing wave to be formed on said second layer which partially overlaps said light incident upon said second surface of said second layer emitted from said first layer, whereby said second layer emits a spot of light on said one surface of said second layer.

17. A method of creating a luminous spot on a surface of a transducer having a first conductor, a first layer of luminescent material in front of said first conductor, a conducting means in front of said first layer of luminescent material, a layer of photoconductive material in front of said conducting means, a second layer of luminescent material in front of said layer of photoconductive material and a second conductor in front of said second layer layer of luminescent material, said conducting means and second conductor being capable of passing light, comprising the steps of:

applying a plurality of electrical pulses having a wave length shorter than the width of said surface of said transducer across said first conductor and said conducting means at a plurality of points on said transducer, whereby a first standing wave of electrical energy is formed between said first conductor and said conducting means such that light is emitted from a portion of said first layer of luminescent material and passed through said conducting means so as to impinge on a portion of said layer of photoconductive material;

applying a plurality of electrical pulses having a wave length shorter than the width of said transducer across said conducting means and said second conductor at a plurality of points on said transducer, whereby a second standing wave of energy is formed between said conducting means and said second conductor;

controlling the time that at least one of said pulses is applied to said transducer with respect to the other of said pulses so that said second standing wave and said light which impinges on said portion of said layer of ph-otoconductive material are partially overlapping; and

controlling the time that at least another of said pulses is applied to said transducer with respect to the other of said pulses so that said spot of light on said surface of said tranducer changes position on said surface of said transducer.

18. A transducer comprising:

a first conductor;

a first layer of luminescent material in front of said first conductor;

conductor means, in front of said first lawer of luminescent material, for conducting electrical energy;

said conductor means being capable of passing light;

a layer of photoconductive material in front of said conductor means;

a second layer of luminescent material in front of said layer of photoconductive material;

a second conductor in front of said second layer of luminescent material;

said second conductor being capable of passing light;

first energization means for applying a plurality of electrical energy pulses having a wave length shorter than the width of said second conductor across said conductor means and said second conductor at a plurality of points on said transducer so as to create a standing wave of electrical energy across a portion of said conductor means and said second conductor;

second energization means for applying a plurality of electrical pulses having a Wave length shorter than the width of said second conductor across said first conductor and said conductor means at a plurality of points on said transducer so as to create a standing wave of electrical energy across a portion of said plied to said transducer, whereby said spot of light is first conductor and said conductor means, whereby moved in position on said transducer.

said first layer of luminescent material emits light from that area between said portion of said first con- References Clted y the Examiner ductor and said conductor means to reduce the re- 5 UNITED STATES PATENTS sistance of a portion of said photoconductlve 2 914 679 11/1959 Loebner 250 213 material; olf-set means for controlling the time that at least one i i of said electrical energy pulses is applied to said 3O59144 10/1962 x 522 transducer'so that said portion of said photoconduc- 10 310297O 9/1963 Haskell 1 25O 213 tive material and said portion of said conductor means and said second conductor partially overlap OTHER REFERENCES Such that Spot of light i from Said Second Windebank, Electroluminescent Display Presents Nanlayer of lum nescent material is smaller than at least osecond Pulses Electronics Dec 8 1961 pp one of said portion of said first conductor and said 15 I conductor means and said portion of said second RALPH GVNILSON, Primary Examiner conductor and said conductor means; and

scanning means for controlling the time that at least STRICKLAND ABRAMSON another one of said electrical energy pulses is ap- 4315mm Examine- 

9. A DISPLAY DEVICE COMPRISING: FIRST TRANSDUCER MEANS FOR EMITTING LIGHT IN RESPONSE TO A FIRST FORM OF ENERGY; SECOND TRANSDUCER MEANS, POSITIONED SO AS TO RECEIVE LIGHT FROM SAID FIRST TRANSDUCER MEANS, FOR EMITTING LIGHT IN RESPONSE TO THE COMBINATION OF LIGHT AND SAID FIRST FORM OF ENERGY; AND ENERGIZING MEANS FOR PROVIDING SAID FIRST FORM OF ENERGY TO SAID FIRST TRANSDUCER MEANS AT A SELECTED AREA, WHEREBY LIGHT WILL BE EMITTED AT THAT AREA, AND FOR PROVIDING SAID FIRST FORM OF ENERGY TO SAID SECOND TRANSDUCER MEANS AT AN AREA WHICH PARTIALLY OVERLAPS THE AREA ON WHICH IT RECEIVES LIGHT FROM SAID FIRST TRANSDUCER MEANS, WHEREBY AN AREA ON SAID SECOND TRANSDUCER RECEIVING BOTH SAID LIGHT AND SAID FIRST FORM OF ENERGY WILL EMIT LIGHT. 